It has been suggested that alcohol consumption may be a risk factor for the development of stroke. I propose to examine two mechanisms by which alcohol could cause stroke - 1) disruption of the blood-brain barrier (BBB) and 2) impairment of endothelial-dependent vasodilation. Despite many studies, it is unclear whether alcohol disrupts the BBB. We will determine whether alcohol disrupts the BBB using a new, quantitative, sensitive microvascular technique and a global quantitative method. We will also determine microvascular mechanisms of disruption of the BBB. It has been demonstrated that alcohol may damage endothelial cells. We propose to do the first studies to determine whether alcohol causes functional damage to the endothelium in cerebral microvessels. These experiments will provide new information on the effect of ethanol on the cerebral microcirculation. We expect that this information will be the basis of future studies on the cerebral vascular effects of alcohol.